The present invention relates generally to an improved alarm control system for actuating an alarm device in response to a warning signal. More particularly, the invention is directed to an alarm control system which automatically resets after each activation to continue sensing subsequent alarm conditions on the premises.
The problem of protecting a premises, and especially premises which are situated in a remote location or periodically unoccupied, against unauthorized intrusions has been one of continuing importance. Various approaches have been taken to this difficult problem, and the prior art contains numerous examples of alarm or warning devices. The earliest forms of such alarm devices were basically of a mechanical nature, such as a trip wire connected between a bell and a door, window, or the like. Relatively crude, these devices have limited capability and require manual resetting after actuation. More recently, sophisticated electronic devices including lamp/photosensors or ultrasonic sources have become popular. These complicated devices, though not necessarily of broader capabilities, are generally expensive to purchase and difficult to install. Some of these prior art devices do not detect an intruder until he is inside the building being monitored. Moreover, many of these electronic alarm devices do not provide for automatic resetting of the device after activation and without manual intervention. Heretofore there has not been available an alarm control system of rugged and inexpensive construction; which can be easily installed by the average owner or occupant; which automatically resets after each activation to continue protecting the premises; and which can be manually activated by the occupants of the premises under a perceived emergency condition.
The present invention comprises an improved alarm control system which overcomes the foregoing and other problems long since associated with the prior art. In accordance with the broader aspects of the invention, a bus line is routed about the interior perimeter of a premises to be protected. A plurality of sensors each positioned near a port of entry to be monitored are connected to the bus line. Each sensor includes line wound on a biased reel and secured at one end to the port of entry. Upon the disturbance of a sensor, circuitry within a master control station connected to the bus line is triggered to activate an external alarm device for a predetermined interval. Following the predetermined alarm interval, the system automatically resets to a ready and armed condition to continue protecting the premises.
In accordance with more specific aspects of the invention, an improved alarm control system incorporating a four conductor bus line leading from a master control station is extended about the interior of a premises. The master control station contains electronic circuitry for energizing the bus line and for activating either an external alarm device or an internal test lamp for a predetermined period of time responsive to warning signals generated by one or more sensors connected in parallel relationship to the bus line. Located near each port of entry to be monitored, each sensor includes a biased supply reel of line which is connected at one end to the port of entry. Movement of any port of entry actuates a magnetically responsive switch within the sensor to transmit a pulse of current triggering timer circuitry within the master control station. Subject to the positioning of a mode switch, either an external alarm or an internal lamp is activated for a preset interval. The system resets automatically after each activation to provide continued protection of the premises without any manual intervention whatsoever.
Preferably, the lines in the sensors are formed of a thermoplastic material, such as nylon monofilament, which would deform under abnormally warm temperature conditions to add a fire detection capability to the system. At least one remote station is connected to the bus line to arm, disarm, or activate the system manually from desired locations within the premises. If desired, a key operated switch can be connected to the system to arm or disarm the system from without the premises.